Chapter 10 - Biodegradation of seafood waste by seaweed-associated bacteria and application of seafood waste for ethanol production

Abstract

A huge quantity of seafood waste is generated from seafood restaurants, fish-processing industries, fish markets, and kitchens every day. The disposal of fish wastes in marine and fresh waters gives rise to an increasing environmental pollution thus adversely affecting the health of aquatic biota. In the present study, nine marine seaweed (Ulva sp.)-associated bacteria capable of calcium carbonate solubilization were isolated from the rocky intertidal region of Anjuna Beach, Goa, India. Out of these nine bacterial isolates, only three were found to utilize 1% crab shell/fish scales/prawn shell powder as a sole source of carbon and nitrogen in seawater-based agar after 10days. These three bacterial isolates were chosen for further investigation and were designated as PM1, PM6, and PM9. Selected bacterial isolates were found to possess phosphate solubilization, cellulase, protease, and chitinase activity. They didn't show cross-inhibition against each other and therefore were used as bacterial consortia for seafood waste degradation study. Consortia showed significant degradation of crab shells, prawn shells, and fish scales within 4days in the seawater-based broth, which was confirmed by DNSA method. DNSA method demonstrated 310±8μg/mL, 245±14μg/mL, and 180±15μg/mL reducing sugars released during degradation of crab shell, prawn shell, and fish scales, respectively, which is considerably high. Based on morphology and biochemical tests, bacterial isolates PM1, PM6, and PM9 were identified as Bacillus sp., Brevibacterium sp. and Vibrio sp., respectively, and through 16S rRNA sequencing, bacterial isolate PM6 was further confirmed to be Brevibacterium iodinum (accession number MG971400). Seaweed-associated bacterial isolates as consortia can, therefore, be employed for biodegradation of seafood wastes. Sugars released during bacterial degradation of seafood waste can be utilized for ethanol fermentation using Saccharomyces cerevisiae.